Along with making size of electric or electronic equipment smaller in recent years, making size of terminals and contact components smaller is underway. For example, in regard to an electrical contact, when the size of a member that constitutes a spring becomes small, the length of the spring is shortened, and thereby, the load stress applied to the copper alloy for spring is increased. When that stress becomes higher than the yield point of the copper alloy material, the material is permanently deformed, and the desired contact pressure as a spring may not be obtained. In that case, the contact resistance is increased, and the electrical connection becomes insufficient, which becomes a serious problem. Therefore, a copper alloy is required to have high strength.
Further, bending workability is generally in a relationship of trade-off with strength. Further, along with making size of electric or electronic equipment smaller, it is necessary to lower the bending radius in bending that is applied to a material. In view of the technical trend of electronic equipment as such, a material having high strength and excellent bending workability is needed.
Further, when each of individual terminals becomes small-sized, there is a problem that the cross-sectional area through which electricity flows is decreased, and a desired current cannot be passed through. For example, a copper alloy that is commonly used as a terminal material is phosphor bronze. However, when the copper alloy has an alloying composition for high strength, the electrical conductivity is around 10% IACS, and this is insufficient for small-sized terminals. Further, when an electronic instrument becomes small-sized, the thermal capacity is reduced, and when the amount of Joule heating of a conductor is high, this is directly related to the overall temperature elevation of the instrument, which is a problem. Therefore, a copper alloy is required to have satisfactory electrical conductivity.
However, the high strength (for example, high yield strength) and the satisfactory electrical conductivity described above are contradictory characteristics in a copper alloy. In this regard, attempts have been, hitherto, made to achieve high strength and satisfactory electrical conductivity in various copper alloys.
Patent Literature 1 proposes that a copper alloy having high strength and satisfactory fatigue characteristics is obtained, by selecting an alloying composition containing the alloying components of a Cu—Ni—Sn-based alloy, and subjecting the alloy to age-precipitation hardening via a particular process.
Patent Literature 2 proposes that a copper alloy having high strength is obtained, by regulating the grain diameter of a Cu—Sn-based alloy and the finish-rolling conditions.
Patent Literature 3 proposes that in the case where the Ni concentration in a Cu—Ni—Si-based alloy is high, the alloy is made to having high strength by preparing the alloy via a particular process.
Patent Literature 4 proposes that a copper alloy having high strength is obtained, by selecting an alloying composition containing the alloying components of a Cu—Ti-based alloy, and subjecting the alloy to age-precipitation hardening via a particular process.
Patent Literature 5 proposes that by obtaining a Cu—(Ni, Co)—Si-based alloy sheet material via a particular production process, the area ratio of the (100) plane facing the RD is increased, the area ratio of the (111) plane facing the RD is decreased, and thereby an alloy is obtained, which has a low Young's modulus of 110 GPa or less in the rolled direction (RD).
Patent Literature 6 proposes that by obtaining a Cu—Ni—Si-based alloy strip via a particular production process, a predetermined {110}<001> orientation density and a predetermined Kernel average misorientation (KAM) value are obtained, and the deep-drawing workability and the fatigue resistance characteristics are enhanced.
Patent Literature 7 proposes that by obtaining a Cu—Ni—Si-based alloy strip via a particular production process, integration to the (220) plane is increased, thus I(220) has a high predetermined X-ray diffraction intensity and a particle size having a predetermined relationship between the transverse (sheet width) direction and the sheet thickness direction, and bending workability is enhanced, which is in the Good Way bending in which the bending axis is perpendicular to the rolled direction.
Patent Literature 8 proposes that when a Cu—Ni—Si-based alloy sheet is obtained via a particular production process, the alloy has the texture having a proportion of the {001}<100> orientation of 50% or more, which alloy does not have any lamellar grain boundaries and has high strength and improved bending workability.